This invention relates generally to reclosable plastic bags and in particular to tape used in the manufacture of reclosable plastic bags, the web that the bags are made from, methods related to their manufacture, and an apparatus for manufacturing reclosable bags that is more efficient and economical than conventional methods and devices.
While most packaging is done with polyethylene sheeting, or a polyethylene sealant layer if barrier sheeting is used, there are problems of sealing the intended sealant layer of the bag wall to reclosable profiles due to profile thicknesses, or due to the thicknesses of flange material that may be integral with the profile, even if the surfaces to be sealed are both polyethylene and compatible.
There are even more complex problems when the sealant layer of the bag walls is something other than polyethylene, as the inside bag wall layer of oriented polypropylene sealant layer of potato chip bags. Sealing reclosable materials to this wall means using materials that are compatible. This invention gives a practical means to accomplish these results.
U.S. Pat. No. 4,909,017, McMahon discloses the delivery of a pair of interlocked, profiled fasteners transversely across a web of film used in forming a plurality of bags. However, the system of McMahon is non-enabling in that fastener strips cannot be delivered as described therein.
There is no attempt in the written description to describe how the narrow fastener strip can be fed, held and sealed onto the base web. The strip material would be unstable for sealing due to the rib and groove design, which would rock on center. The strip material is naturally curled from extrusion and distorted from being wound onto a spool. The difficulty of feeding this unstable strip cross web, remove curls and twists, stretch straight and hold for heat and pressure application between a seal bar and anvil makes this method chaotic and impractical.
There are at least two other major shortcomings of the McMahon ""017 patent. The first shortcoming involves the impossibility of making commercially acceptable seals of the bag walls to the backside of each fastener half in the bagger sealing jaws. The second shortcoming involves the window of registration required to seal the backside of the fastener to a finished bag wall during bagger cross sealing and the inability of known form fill seal and equipment to repeat the bagger film draw with the required accuracy.
Specifically, the McMahon ""017 patent describes a pressure bar seal in the bagger sealing jaws that seals the outer bag material precisely to the backside of the fastener profile. Yet, it has been discovered, as described in Applicant""s specification, that a pressure bar seal requires a stable and flat surface to properly seal. The irregular shape of the fastener profile makes this impossible. One requires heat, dwell time, and pressure to effect a commercially acceptable seal and due to the irregular shape of the profile, it is impossible to get enough stable pressure to accomplish a commercially acceptable seal. The surface moves and gives unpredictably. If enough heat and pressure are applied for a sufficient dwell time to mash the base of the profile flat enough to seal, the profile hooks are softened and deformed, making it impossible to repeatedly use the completed bag for opening and reclosing.
The McMahon ""017 patent has an additional shortcoming related to sealing the seamed side of the bag to the opposite side of the fastener. Based on Applicant""s knowledge and experience, this cannot be done to produce a commercially acceptable product. The fact is that no bagger can draw with the accuracy the McMahon ""017 patent requires, to place the second seal, in register, on the back side of the fastener profiles.
Another illustrative patent is U.S. Pat. No. 5,461,845 to Yeager. There are at least two definitive shortcomings therein. The first shortcoming relates to the problem of having to open the zipper completely from the front panel of the finished bag. Users of reclosable bags and packaging are accustomed to opening the profiled fastener from the xe2x80x9ctopxe2x80x9d of the package, and not from the front panel of the package. Hence, the user will have to become accustomed to a method with which he may not be familiar or comfortable.
The second shortcoming is more serious, and relates to the requirement of opening the package from the front panel thereof. If the package is to be opened from the front panel, a cut or perforation must be made before the fastener is applied. This cut, or perforation, is generally shaped like an xe2x80x9covalxe2x80x9d with opening xe2x80x9ctabsxe2x80x9d for gaining access to the fastener. Since the fastener, most likely, is not closed at the ends of the fastener, the possibility of contamination exists.
The most expedient and economical way to make the package is to create the cut, or perforation, in one operation, just upstream of the fastener strip application. This operation, in its simplest form, will leave openings for potential contamination to pass through the cut or perforated, front panel opening. To overcome this contamination potential, users of this method add a great deal more cost and complexity to create a sealed, sealable xe2x80x9cpatchxe2x80x9d, or some other means of eliminating this contamination risk. The same problem occurs, if the package must be hermetically sealed.
There is also a serious drawback of coextroding a flanged zipper having ribs on the inside of the flanges so that it is unsealable, when heat is applied to each bag wall side. The drawback is that a unitary extruded flanged zipper has a limitation as to thinness of the flanges that can be integrally extruded with reclosable profile. Further, use of co-extruded ribs to make the inside of the flanges not seal together increases the thickness of the flange area even more.
This contrast in thickness of the 4 layers of material which includes the 2 bag walls and the 2 zipper flanges will make it virtually impossible to blend the cross seals through the 4 thickness area and into the 2 thickness area of the bag walls only. For example, if a 3 millimeter: i.e., xe2x80x9cmilsxe2x80x9d wall bag is being made, the coextruded flange with ribs, will be 16 mils per side or 32 mils total. This would require a blending of 38 mils to 6 mils and would most likely eliminate the possibility of closing off openings in the folds of any bag made on a vertical FFS machine.
Thus, there exists a need to solve the problems in the art that are articulated above.
Accordingly, it is an object of the invention to overcome the shortcomings of the prior art by providing a large skirt (tape) area which a second seal can be easily registered. The skirt (tape) height of the area could be changed, depending upon the bagger design, condition, and the variation in draw height of the bagger.
It is another object of this invention to overcome the shortcomings of the art by using fastener profile mounted on tape in the bag forming process, and requiring that the operations involved sealing two flat, substantially parallel thin surfaces. Thus, there is no irregular surface that is sealed to attach the fastener to the front panel, or to carry the fastener through the bagger and down the form, fill and seal tube or to seal the back-seamed side of the package. It is also an object of the present invention to allow the customer/user of the package to open the package from the top, as he or she is accustomed.
It is an additional object of the invention to treat the inside surface of the skirt (tape) area to prevent area from being sealed together in the process described below, to allow zipper and bag opening from this area.
It is an additional, object of the invention to solve the shortcomings of the art through the use of fastener tape as described below, to provide a thin substantially flat, fastener appendage which is sealed to the bag wall(s) and to treat the inside layers of the fastener opening tabs, above the fastener.
It is a further object of the invention to provide an automatic contamination-free package by sealing the fastener completely inside the package. In this variant, the top seal of the package must be cut off to allow the customer/user to get to the opening tabs of the fastener.
It is a further object of the invention to provide improved control of web dispensing by using driven, dancered unwinding of the base web and indexing of the base web for zipper application positioning. The zipper application includes a servo motor and computerized motor controls.
It is an additional object of the invention to provide unwinding, tensioning, guiding and indexing of the fastener tape materials in the attachment thereof to a web, linked to the indexing of web but independent thereof.
It is a further object of the invention to obtain a balance of tensions between the fastener strip and tape material by providing a driven, dancered web for feeding folded and lightly-tensioned tape material to a fastener sealing device.
It is yet a further object of the invention to obtain a flatter, straighter, curl-less fastener tape from the fastener tape operation by more accurately controlling the relative tensions of the webless fastener and the tape material during application of the fastener material to the tape.
It is another object of the present invention to solve these and other problems in the art, and to serve a market that demands hundreds of millions of reclosable plastic bags annually. The objects and features of the present invention, other than those specifically set forth above, will become apparent in the detailed description of the invention set forth below and in the drawings.
The invention also provides a method of making a reclosable bag having a body with top and bottom ends and opposing walls in a vertical, form, fill and seal machine that includes the steps of forming the bag walls from web material having a longitudinal back seal extending between the top and bottom ends of the bag body, and transversely securing across the longitudinal back seal a flange of a flanged, interlocked fastener strip. The flange is substantially wider than the width of the interlocked fastener strip attached to the flange. As such, it is appreciated that the sealer bars do not contact or deform the interlocked fastener strip during the sealing process. It is further appreciated that the method allows for a commercially acceptable seal to be made across the longitudinal back seal while providing greater tolerance for deviations in bagger web draw.
The flange or tape is sized and dimensioned to provide a larger window of registration than that required to seal the backside of a conventional fastener onto a finished bag wall whether it is a back or front panel wall, directly onto the backside of the fastener during bagger cross sealing. The flange or tape is also sized and dimensioned to provide repeatable sealing of the tape or flange to the bag wall during the transverse bagger cross sealing process while allowing for variances and deviations in bagger web draw.
The invention further includes an improved vertical, form, fill and seal process that includes transversely sealing a non-profiled, stable and substantially flat surfaced appendage or flange having a profiled, interlocked, reclosable fastener strip connected thereto across the longitudinally extending back seal of a bag during bagger cross sealing. It is appreciated that the transverse sealing across the non-profiled, stable and substantially flat surfaced appendage permits one to seal the appendage to bag material with an effective heat, dwell time, and pressure to effect a commercially acceptable seal without the surface moving and giving unpredictably. It is also appreciated that greater, pressure and dwell can be applied to mash the shape flat enough to seal, while simultaneously preventing the profiled fastener from softening and deforming making it possible to repeatedly use the completed bag for opening and reclosing.
In a variant, as described above the invention provides a two piece tape or flange comprising a very thin, substantially flat, tape or flange portion connected to the zipper profiles to obtain a commercially acceptable flanged zipper. The very thin, substantially flat, tape or flange portion is preferably construct from web material of about 0.003xe2x80x3 in thickness that is very flexible. It is also possible to use tape materials in the range of about 0.003xe2x80x3 inches in thickness to as thin as 0.001xe2x80x3 in thickness. The preferred loop is a high loop of about 1.25xe2x80x3. By using a high loop it is possible to obtain enough stiffness in the combination tape/flange fastener profile assembly to push the assembly at the start of the transverse application process, and then attach the thin, flexible, wide loop quickly to a vacuum belt, so that it can be carried across the base web for positioning. Holding and transporting the flexible loop (or flange if the loop is split open) across the web is readily accomplished using a modest amount of vacuum. A printed barrier can be applied to the inside loop area to make it non-sealable, while adding very little to the thickness of the loop.
The system method, and (tape or flange) assembly described above is extremely versatile. The tape or flange is substantially thin allowing its use with a greater variety of bag walls materials, regardless of the base web thickness. The tape or flange, since it is ribless and thin, blends the cross seals better, from tape plus bag wall thickness to bag wall thickness only, and results in continuous seals, sealed in the bagger sealing jaws.
Further, the assembly described above is constructed to be readily, transversely xe2x80x9cpulledxe2x80x9d across a web of material, and the assembly method, and system can be used with any appropriate tape base material. As described above. the invention described above can be used on laminate bag wall base web material, e.g. snack food bag wall and base web material where a user does not want to change their present structure/bag wall material which would not seal to LDPE material. The preferred non-sealable treatment of the tape or flange is to provide a printed food grade nitro cellulose coating into the loop (flap) area. As such, the invention provides a two-piece fastener profile having each respective profile connected to a loop portion of a tape or flange in which the inside loop portion of the tape or flange is treated to be non-sealable, e.g. has a non-sealing inside surface.